Knee Extensor Lag Versus Lack: Understanding the Difference

Abstract

This chapter provides a comprehensive analysis of knee extensor lag and knee extension lack (contracture), two different conditions affecting knee joint mobility. Extensor lag occurs when active knee extension is limited despite a full passive range of motion, often resulting from quadriceps insufficiency, neuromuscular impairment, or pain inhibition. In contrast, extension lack is a structural restriction preventing both active and passive extension, commonly due to soft tissue contractures, intra-articular adhesions, or osteoarthritis. Key assessment techniques include active and passive extension tests, goniometric measurements, and palpation methods to differentiate between these dysfunctions. The chapter discusses post-surgical complications, neurological deficits, and biomechanical factors contributing to these conditions. Understanding the difference is essential for accurate diagnosis and effective rehabilitation, ensuring targeted physical therapy, strengthening protocols, and surgical interventions where necessary.